While many solar energy collectors have been proposed in the prior art, most have been deficient in working efficiently over long periods of time, and have required extensive maintenance. In most cases the collectors have been expensive, and have been restricted to use in limited applications.
Concave reflector type collectors have been well known and these are adaptable for use with servo systems that track the sun as shown for example in U.S. Pat. No. 4,038,971 issued Aug. 2, 1977 or U.S. Pat. No. 4,061,130 issued Dec. 6, 1977. It is desirable for optimum efficiency to direct solar energy collectors toward the sun and to track the sun to receive the maximum solar energy into the collector.
A serious problem with efficiency and longevity of use of solar collectors between maintenance periods is to keep reflector surfaces and transparent windows clean and free of interfering films and dirt. It has been proposed that solar collectors be self-cleaning by means of running water in U.S. Pat. No. 3,785,931 issued Jan. 15, 1974. It is not feasible, however, to provide running water to cleanse the surfaces in most practical operation conditions, and further the water itself carries substances that make films and decrease reflectivity.
In order to increase efficiencies in solar furnaces which concentrate solar rays upon a pipe carrying liquids to be heated, it is known that the effective heat absorbing area of the pipe can be increased with fins or the like as shown in U.S. Pat. No. 4,092,979 issued June 6, 1978. Also in this and other patents blackened pipe surfaces have been used for more efficient heat absorption to prevent reflection off the pipe and loss of the available heat.
It is the object of this invention to improve the state of this solar energy collector art by providing inexpensive and efficient solar energy collection means in an improved combination of elements coacting together to utilize solar energy.
Other more specific objectives of the invention are to (1) collect rays and transport materials heated by the rays at temperatures greater than 100.degree. C.; (2) to avoid losses inherent in most collectors because of reradiation and convection losses from wind and reflection, etc.; (3) to provide means for keeping the reflective surfaces clean avoiding accumulation of films and dirt which reduce solar energy conversion efficiencies; (4) to provide a substantially maintenance free system that retains its conversion efficiencies over long time periods; (5) to improve collection efficiencies; and (6) to keep construction simple and inexpensive using low cost common materials and manufacturing techniques.